The present invention relates to fiber optic communications networks, and more particularly to a configurable safety shutdown for an optical amplifier using non-volatile storage for system configuration for reliably controlling a safety shutdown function in the event of a fiber optic transmission line disconnect or cut.
The demand for communications capacity on fiber optic communications networks has resulted in increased use of wavelength-division multiplex (WDM) systems. WDM systems provide another level of multiplexing to individual or already multiplexed channels. In WDM systems, the individual transmission channels are carried on separate optical wavelengths and are combined in a single fiber at the optical link layer. WDM systems are generally used when the number of fibers in a transmission link is inadequate for the capacity or becomes a critical cost item.
The distances between WDM optical equipment and the signal transmission rates may be attenuation and/or dispersion limited. As a result, amplifiers are employed to boost signal strength to overcome these limitations due to losses from WDM devices, dispersion compensating fibers/gratings, connectors, splices, and fiber. As amplifier designs and WDM systems have evolved, so has the need for increased power grown. Optical power levels generated by fiber optic transmission systems can therefore be high enough to be hazardous to the human eye. If the transmission fiber is disconnected or accidentally cut or broken, the open end of the fiber can be emitting hazardous power, and this emission can possible be pointed into a person""s eye. This power is higher when multiple optical channels are transmitted over a single fiber, as in WDM systems. Even higher power levels are generated when optical amplifiers are used.
Fiber optic transmission systems may employ a safety shutdown function which will shut down the optical output when the fiber is disconnected, cut, or broken. Such existing safety shutdown systems are based on the detection of input loss of power, which is then used to shut down the optical output. The operation of an optical amplifier is controlled by various parameters including, for example, shutdown, restart off period, restart on period, and loss of signal threshold. These parameters allow optical amplifiers within the optical transmission system to be configurable, depending upon the specific application and location within the system. Configuration and reconfiguration of such parameters within an optical amplifier may be accomplished by utilizing system software to configure logic gates within an optical amplifier module. However, due to the use of volatile software configurable logic gates, there exists the possibility that the gates may be accidentally reprogrammed to a configuration which makes the optic transmission system unsafe. Such undesirable changes may occur when a module is removed from the system and reinserted in a different location or plugged back into a same location. Furthermore, internal system software changes may occur to reconfigure an optical amplifier without knowledge of a system operator.
A need has thus arisen for a system for reliably configuring an optical amplifier safety shut down function in a fiber optic transmission network where the network may utilize configurable optical amplifiers such as, for example, erbium-doped fiber amplifiers (EDFAs) and other remote pumped EDFAs for boosting signal strength in WDM systems to ensure proper amplifier configuration.
In accordance with the present invention, in a fiber optic communications network having an optical amplifier including a safety shutdown input, a system for configuring the optical amplifier is provided. The system includes a non-volatile memory for storing optical amplifier parameters. Circuitry is provided for inputting amplifier parameters into the memory and for changing previously stored amplifier parameters. Configuration of the optical amplifier parameters cannot be changed until a hardware control input is actuated via manual intervention. The system also provides for an indication of a mismatch between newly input parameters and previously stored optical amplifier parameters.